Overall survival for patients with melanoma that has spread to the brain is only four to six months. Researchers have therefore investigated a new therapeutic approach to more effectively target melanoma in the brain. The therapy devised by the scientists uses a “twin stem cell model” designed to maximize an attack on cancer cells that have spread to a part of the brain known as the leptomeninges. A stem cell releases a cancer-killing virus (oncolytic). Using stem cells to deliver the virus amplifies the amount of virus that can be released, and ensures that the virus will not be degraded by circulating antibodies before it is released on cancer cells. However, the oncolytic virus also destroys the cells that release it, making it an unsustainable therapeutic option. Therefore, scientists have used CRISPR/Cas9 gene editing to create a second stem cell that cannot be targeted by the oncolytic virus and instead releases proteins (immunomodulators) that boost the immune system to help fight cancer. Twin stem cells can be delivered by intrathecal injection. Unlike other immunotherapies that have appeared in recent years, it does not need to be administered repeatedly. The researchers point out that this approach can be used in other cancers with metastases.
